[Samba] Strange crashes and disconnection from PDC?

[Andrew Bartlett]

Nir Soffer wrote:
> 
> Cc:'d to samba-technical
> 
> ( Background - I'm trying to see how I can get smbd to dump core,
>  with a user supplied option to allow tell it where to dump it, I'm
>  poring over the related code)
> 
> > A 'corefile directory' option might be nice - but we will have to be
> > careful.  Look into smb_panic() and exit_server() for somewhere to
> > start.
> 
> Err. Okay. Can anyone explain me what's up here? From server.c
> 
> #if DUMP_CORE
> /*******************************************************************
>  Prepare to dump a core file - carefully !
> ********************************************************************/
> 
> static BOOL dump_core(void)
> {
>         char *p;
>         pstring dname;
>         pstrcpy(dname,lp_logfile());

You certainly could not use this in a signal handler, becouse it just
touches too much of (the already possibly corrupt) smbd.

>         if ((p=strrchr(dname,'/'))) *p=0;
>         pstrcat(dname,"/corefiles");
>         mkdir(dname,0700);
>         sys_chown(dname,getuid(),getgid());
>         chmod(dname,0700);
>         if (chdir(dname)) return(False);
>         umask(~(0700));
> 
> dump_core is already there, DUMP_CORE is set to 1 (it looks like this
> is the default one shipped, btw), yet nothing bloody happens.
> 
> The above snippet appears to create a corefiles directory above the log
> dir, (which is, I assume, what you want to change using the core
> directory
> option), but it doesn't create it anywhere I can see after killing a
> process with
> sig11. What am I missing here?
> 
> Also - from what I see, the execution flow of a panic is something like:
> 
> exit_servers is set is a fault handler, however in fault_setup (fault.c)
> a
> SIGSEGV handler is set to sig_fault which calls fault_report which
> calls smb_panic which calls abort().
> 
> When the heck is exit_servers called, then? And what function does
> dump_core perform if there's no one to call it?

I think it's there for gprof runs.  You extract the profile data by
dumping core and exaimining the resulting binary...

> I'm probably missing something fundamental here, enlightment will
> be appreciated.

Yes, its a weird area...

Andrew Bartlett

-- 
Andrew Bartlett                                 abartlet at pcug.org.au
Manager, Authentication Subsystems, Samba Team  abartlet at samba.org
Student Network Administrator, Hawker College   abartlet at hawkerc.net
http://samba.org     http://build.samba.org     http://hawkerc.net